Flotation apparatus



Dec. 12, 1961 Filed Aug. 51, 1959 H. u. ZIEMER FLOTATIIYON APPARATUS 4Sheets-Sheet 1 [77%]? for: 1%2225 ll Zienzer Dec. 12, 1961 H. u. ZIEMERFLOTATION APPARATUS Filed Aug. 51, 1959 4 Sheets-Sheet 3 fiflfeizzor.flaws U Zz'eilyer 15: W a M orneg United States Patent Ofiice 3,012,671Patented Dec. 12, 1961 3,012,671 FLOTATION APPARATUS Hans U. Ziemer,Lakeland, Fla, assignor to International Minerals & ChemicalCorporation, a corporation of New York Filed Aug. 31, 1959, Ser. No.837,238 5 Claims. (Cl. 209170) The present invention generally relatesto the art of beneficiating materials by flotation techniques. Moreparticularly, it relates to a novel apparatus for beneflciating ores andother substances by flotation.

The beneficiation of ores by froth flotation techniques is of greatimportance to the ore beneficiation art. The flotation process is widelyused for treating metallic and non-metallic ores and, in addition, isreceiving an ever widening application in other industries.

In many of the prior art flotation machines the mineral feed, which isusually in the form of an aqueous pulp, is introduced horizontally intoa flotation cell which is usually constructed substantially in the formof a cylinder or prism. The pulp is agitated and aerated in theflotation cell by a rapidly rotating impeller which rotates on asubstantially vertical axis. The mineral-laden air bubbles separate fromthe other material and pass upwardly to the pulp level of the flotationcell to form a froth which is floated off the top of the cell.

Since the pulp is introduced laterally into such a flotation cell, inwhich the air bubbles are passing chiefly in an upward direction, it hasbeen difficult because of this diflerence in the directions of flow toobtain a uniform distribution of air bubbles throughout thecross-section of the cell. It has also been difficult to float mineralparticles of relatively large mass in such a flotation cell.

A different type of flotation cell has recently been developed whichremedies some of the shortcomings of many of the prior art flotationmachines. This new flotation cell is described in detail in copendingU.S. patent application Serial No. 754,765, filed August 13, 1958, nowU.S. Patent No. 2,922,521, issued January 26, 1960. The apparatusdescribed in the copending patent application includes an inlet conduitfor containing a flowing stream of fluid, and a laterally divergingvertical conduit connected to the inflow conduit adjacent the outflowend thereof for receiving the flowing stream of fluid from the inflowconduit. The laterally diverging conduit comprises a part of theflotation cell. A pump is connected in the inflow conduit line forpumping the flotation cell feed through the inflow conduit into thelaterally diverging conduit. The present invention is directed toimprovements in such flotation apparatus. When using such apparatus, ithas been possible, because of air and pump thrust upwardly'into thediverging conduit, to eflect a higher weight recovery of materials thancan be obtained in more conventional flotation cells; for example, suchcells as are used in Fagergren and Denver flotation machines. Intheflotation apparatus described in application Serial No. 754,765, theaerating air is mixed with the aqueous pulp in the pump and the airpulpmixture is directed into the flotation cell. it has, however, beendifficult to control the quality and quantity of aeration when usingsuch apparatus and the present invention provides an apparatus in whichthe aeration is readily controlled.

It is, accordingly, an object of the present invention to provide anovel apparatus for beneficiating. ores.

It is a further object of the invention to provide a new flotationapparatus which achieves eflicient aeration in the flotation cell.

It is another object of the invention to provide a new flotation machinehaving a diverging conduit flotation cell with aerating means providedbetween the diverging walls of the cell.

These and further objects and advantages of the present invention willbe apparent from the following description and accompanying drawingswhich illustrate embodiments of the invention.

In the drawings:

FIGURE 1 is a side elevational view, partially broken, of one form offlotation apparatus embodying certain of the features of the invention;

FIGURE 2 is a plan view of the apparatus illustrated in FIGURE 1;

FIGURE 3 is a sectional view taken substantially along line 3-3 ofFIGURE 2;

FIGURE 4 is a plan view of a flotation cell, generally similar to thatillustrated in FIGURES l to 3, embodying another form of aerating means;and

FIGURE 5 is a sectional view taken substantially along line 55 of FIGURE4.

As will hereinafter appear, the above-stated objects of the inventionare accomplished by the provision of aerating means in the divergingconduit system of a flotation cell. The invention makes possible morepositive and more effective control of the quality and quantity ofaeration in diverging conduit flotation cells than has heretofore beenattained.

The apparatus of the present invention is eminently use- ,ful for thefroth flotation beneficiation of potash ores such as sylvite, sylvinite,langbeinite, mixed potash ores, etc, phosphate ores, and the like. Theapparatus operates efliciently at high throughputs. The apparatus alsomakes possible the beneficiation of larger ore particles than areusually beneficiated in conventional flotation machines.

In general, the flotation apparatus of this invention comprises aninflow conduit for containing a flowing stream of fluid, a laterallydiverging conduit connected to the inflow conduit adjacent the outflowend thereof for receiving the stream of fluid from the inflow conduit,and aerating means between the walls of the diverging conduit. Byproviding aerating means in the diverging conduit systern, moreefficient aeration of the pulp is achieved and the quality and quantityor aeration may be readily 'controlled. It is to be understood that theparticular structures illustrated in the drawings are merelyillustrative embodiments of the general principles involved.

The apparatus provides a flotation cell having a bottom inlet and anoverflow adjacent to the upper end of the flotation cell. Between theinlet and overflow,,the flotation cell is defined by a rigid-walledlaterally diverging cell. The aerating means between the diverging wallsof the flotation cell control the quality and quantity of -aerationindependently of the feed rate and other variables in the flotationoperation. The inflow conduit opens centrally or substantially centrallyinto the flotation cell from below and the pulp-air mixture emerges fromthe inlet pipe as a jet stream and rises in the flotation cell. Theair-laden mineral particles continue to rise in the cell to the frothlevel.

Since the jet stream carries the solid entrained particles mainlyvertically upwardly in the same direction that the air bubbles arerising, the adherence of the solid particles to the air bubbles isgreatly facilitated and at the same time a shaking or shearing of thesolid particles from the bubbles is substantially reduced. For thisreason, the apparatus enables a reliable flotation of even unusuallycoarse particles with high efficiency.

The flotation cell is also provided with an outflow conduit connected toa lower portion of the cell through which non-floated material may bewithdrawn from the cell. A control valve is connected in the outflowconduit and the control valve is operatively connected to the fluid inthe flotation cell.

A flotation apparatus embodying the principles of this invention isillustrated in FIGURES l, 2, and 3 of the drawings. Another embodimentof the aerating means is illustrated in FIGURES 4 and 5 of the drawings.In both embodiments, many of the pieces of apparatus are the same andcorresponding numbers are used. Referring to the drawings, the apparatusillustrated includes an inflow conduit 11 which is connected to thebottom of a rigid walled, laterally diverging conduit or flotation cell13. The flotation cell 13 is illustrated as an inverted pyramid having arectangular cross section; however, the diverging conduit may take onother forms such as an inverted cone. The point angle of the cell ispreferably from about 20 to about 50. The cell also preferably has aheight from about 1.5 to about 3.5 times the width of the cell. The cell13 has a substantially vertical axis and the walls thereof divergelaterally with increasing elevation. The inflow conduit 11 is also adischarge conduit of a pump 15. The inflow conduit 11 extends verticallyupwardly and has an extension 17 (FIGURES 3 and 5) into the flotationcell. In general, the length of the extension 17 into the flotation celldepends upon the feed rate and the ratio of floated material tonon-inflated material. For example, when beneficiating differentmaterials at substantially the same inflow conditions, if the ratiochanges from 1:2 to 1:4, the extension 17 is preferably of relativelylonger length in the latter operation. The flotation cell 13 is providedwith an inclined bottom 19 spaced below the outlet opening of theextension 17. The flotation cell 13 also has connected adjacent itslowermost point an outflow conduit 21 through which material may bewithdrawn from the flotation cell. In order to etflciently drain theflotation cell when the cell is not in operation, the lower part of theoutflow conduit 21 is in substantial alignment with the inclined bottom19 and is connected into the flotation cell 13 at the lowermost point ofthe inclined bottom 19.

The flotation cell 13 is provided at the top with vertical walls 23, 25,27 and 29 which together form a froth box on the flotation cell 13. Theupper edge of the inside wall 29 is somewhat lower than the upper edgeof the other walls and provides a froth discharge means from theagitation cell 13. An overflow weir 31 is suitably fixed in wall 29 andextends above the upper edge of this wall. The weir 31 is preferablyadjustable in height by means not shown. A guide plate 33 is connectedto the top edge of the wall 29 and curves downwardly to a funnel 35. Thefunnel 35, illustrated, is also of rectangular cross section and theupper edge of the inside vertical wall 37 of the funnel is connected tothe guide plate 33. The funnel 35 has four vertical walls which form afroth box on the funnel. The inside wall 37 and the outside wall 41 areparallel. The other two parallel walls are extensions of walls 23 and 27of the flotation cell 13, and, therefore, the same numbers designatethese walls. The four vertical walls together form a froth box on thefunnel 35.

The wall 41 is somewhat lower than walls 23 and 27 and is provided atits top edge with a chute 39, which receives the discharge froth fromthe froth box of the funnel and delivers it to a discharge trough 42.The wall 41 is preferably provided on the inside with a weir 43 which ispreferably vertically adjustable by means not illustrated. The top edgeof the weir 43 is provided with a downwardly and inwardly inclined plate45 over which a rotatable paddle wheel 47 is positioned. When inoperation, the paddle wheel 47 rotates in the direction shown by thearrow A in FIGURES 3 and 5, which aids in moving the froth out of thefunnel and into the discharge trough 42. A recycle conduit 49 connectsthe bottom of the funnel 35 to a fresh feed inlet conduit 53 which isconnected to the suction end of the pump 15. An air inlet conduit 55 isalso connected into the fresh feed inlet conduit 53. This conduit 55 hasa throttle flap 57 therein for regulating the flow within the conduit55. Aerating air is introduced into inlet conduit 53 via conduit 55 toaerate the aqueous pulp being drawn into the suction end of the pump 15.

As illustrated in FIGURES 2 and 3, the aerating means provided includesthree aerating rings, 59, 61, and 63, positioned within the walls of thediverging conduit flotation cell 13 above the outflow end of theextension 17 and below the overflow from the cell. These rings arevertically spaced within the diverging walls. These aerating meanseffect etficient aeration of the aqueous pulp in the flotation cell 13.Each of the aerating rings, illustrated, is a circular hollow tube. Inorder to effect substantially uniform aeration across a horizontal crosssection of the flotation cell, the upper ring 63 is of greater diameterthan the middle ring 61 and, similarly, the diameter of the middle ring61 is greater than the diameter of the lower ring 59. The rings aresubstantially horizontal and the diameter of each ring is preferablysuch that the outside portion of each ring passes adjacent to thediverging walls; however, the rings may be of smaller diameter. Theinterior of each of the tubular rings is connected to a source ofpressurized air (not illustrated) by a tube 65 which projects throughthe wall of the cell 13. In order to regulate the quantity of airpassing into each of the tubular rings, 59, 61, and 63, a valve 67 ispositioned in each of the tubes 65. Each of the aerating rings has aplurality of spaced holes 69 therein which permit the air within thetubular rings to pass into the flotation cell, thereby providing aplurality of aerating points in the cell. The size and number andspacing of the holes or openings 69 may vary with the particularmaterial being processed, the processing conditions, etc. In general,the holes are equally spaced and in the upper part of each tube so as toprovide a plurality of upwardly directed jets of air into the cell.

In the embodiments illustrated in FIGURES 4 and 5, the aerating meansincludes a plurality of holes extending through the walls of theflotation cell. Three sets of holes, 71, 75, and 79, each set being at adifferent elevation in the cell 13, are provided in the flotation cellso as to achieve substantially uniform aeration across a horizontalcross section of the cell 13. Each set of holes includes a plurality ofholes at substantially the same elevation. The lower series of holes 71are substantially equally spaced and are present in each of the fourwalls of the flotation cell 13. The middle set of holes 75 is positionedabove the lower set 71 and the holes in this middle set are also equallyspaced around the four walls of the cell 13. The same is true of theupper set of holes 79. In order to achieve individual control over theamount of aeration being affected by each of the series of holes, eachseries is separately connected to a source of pressurized air (notshown). Referring to the lower series of holes, 71, a jacket 81 isprovided on the exterior of the flotation cell 13 so as to enclose theholes 71. The jacket 81 is continuous and is secured, as by welding, tothe exterior of the flotation cell 13 so that air does not leak outbetween the jacket 81 and the exterior walls of the flotation cell 13.The air chamber provided between the walls of the conduit 13 and thejacket 81 is in fluid communication with a source of pressurized air(not shown) through pipe 83. A valve 85 is positioned in pipe 83 as asto permit the control of the quantity of air being introduced into theflotation cell through the holes 71. In a similar manner, the middleseries of holes 75 is in communication with the air chamber formedbetween the flotation cell 13 and a jacket 87. This air chamber isconnected to a source of pressurized air via pipe 89 in which valve 91is positioned. In a further similar manner, the upper series of holes 79is connected with the air chamber provided between the walls of theflotation cell 13 and a jacket 93. This air chamber is in fluidcommunication with a source of pressure air via pipe 95 which has avalve 97 therein.

In the embodiment illustrated in these figures, three series of holesare illustrated at diiferent elevations in the diverging conduit systemof the flotation cell. It is to be understood, however, that one, two,three or more of such series of holes may be used. In general, with moreaerating holes, a more uniform aeration of the pulp in the flotationcell is achieved. Also in the illustrated embodiments the air suppliedto each of the rings 59, 61 or 63, or to the series of holes 71, 75, and79 is individually controlled. Individual control, while preferred, isnot an essential feature.

A control valve 99 (FIG. 1) is positioned in the outflow conduit 21through which tailings may be withdrawn from the flotation cell 13. Ithas been determined that the operation of the flotation cell may beefficiently controlled by controlling the rate of tailing withdrawalthrough the outflow conduit 21. The control valve 99 adjustably controlsthis rate of withdrawal. The control valve 99 is operatively connectedto the fluid in the flotation cell 13. The operation of the flotationcell 13 is preferably controlled by adjusting the rate of tailingwithdrawal so as to maintain a substantially constant predetermined pulpdensity in the flotation cell and preferably in the lower portion of theflotation cell. The control valve 99 is, therefore, preferablyoperatively connected to the interior of the cell, that is to the fluidin the lower portion of the flotation cell 13, in a manner to obtain asubstantially constant predetermined pulp density in the lower portionof the cell 13. The control valve is preferably rubber lined so as toreduce corrosion of the valve. In the illustrated embodiment, theopening or closing of the control valve 99 is controlled by an automaticcontrol device 101 (FIG. 1) which is diagrammatically illustrated in thedrawing since such devices are well known and the specific constructionof the device 101 forms no part of the invention. The control device 101is operatively connected to the valve 99 by line 103. The control device101 is also operatively connected to the material in the lower portionof the flotation cell 13 by line 105. The device 101 receives a signalthrough line 105 which is proportional to the pulp density in the lowerportion of the flotation cell and the control device 101 converts thesignal into a form which adjusts the amount of opening of the controlvalve 99 thereby adjusting the rate of withdrawal of tailing through theoutflow conduit 21. The control valve 99 is controlled by the controldevice 101 in a manner such that when the pulp density in the lowerportion of the flotation cell is above the predetermined pulp densitywhich it is desired to maintain, the valve is in a relatively more openposition and the rate of withdrawal of pulp through line 21 is greaterthan when the pulp density is at the predetermined density. Similarly,the control valve 99 is controlled by the control device 101 in a mannersuch that when the pulp density in the lower portion of the flotationcell is below the predetermined density which it is desired to maintain,the valve 99 is in a more relatively closed position and the rate ofwithdrawal of pulp through conduit 21 is less than when the pulp densityis at the predetermined point.

The description of the invention utilized specific reference to certainconstruction details; however, it is to be &

understood that such details are illustrative only and not by way oflimitation. Other modifications and equivalents of the invention will beapparent to those skilled in the art from the foregoing description.

Having now fully described and illustrated the invention, what isdesired to be secured and claimed by Letters Patent is set forth in theappended claims.

I claim:

1. Flotation cell apparatus comprising a vertical rigidwalled laterallydiverging conduit having a substantially centrally positioned bottominlet and an overflow adjacent to the upper end, a substantiallyvertical inflow conduit connected to the bottom inlet of said divergingconduit for introducing a stream of fluid vertically upward into saidflotation cell, and aerating means carried by the diverging conduitadjacent the conduit wall and providing a plurality of generallyhorizontally arranged apertures encircling said stream of fluid, saidaerating means being disposed above the outflow end of said inflowconduit and below said overflow to effect a distribution of air bubblesacross a horizontal cross section of the cell when the flotation cell isin operation.

2. Flotation cell apparatus comprising a vertical rigidwalled laterallydiverging conduit having a substantially centrally positioned bottominlet and an overflow adjacent to the upper end, a substantiallyvertical inflow conduit connected to the bottom inlet of said divergingconduit for introducing a stream of fluid vertically upward into saidflotation cell, an outflow conduit connected to a lower portion of saidflotation cell, and aerating means, carried by the diverging conduitadjacent the conduit wall and providing a plurality of generallyhorizontally arranged apertures encircling said stream of fluid, saidaerating means being disposed above the outflow end of said inflowconduit and below said overflow to effect a substantially uniformdistribution of air bubbles across a horizontal cross section of thecell when the flotation cell is in operation.

3. Flotation cell apparatus comprising a vertical rigidwalled laterallydiverging conduit having a substantially centrally positioned bottominlet and an overflow adjacent to the upper end, a substantiallyvertical inflow conduit connected to the bottom inlet of said divergingconduit for introducing a stream of fluid vertically upward into saidflotation cell, an outflow conduit connected to a lower portion of saidflotation cell, aerating means carried by the diverging conduit adjacentthe conduit walls and providing a plurality of generally horizontallyarranged apertures encircling said stream of fluid, said aerating meansbeing disposed above the outflow end of said inflow conduit and belowsaid overflow to effect a distributionof air bubbles across a horizontalcross section of the cell when the flotation cell is in operation, saidaerating means including at least one circular tubular member providingsaid plurality of apertures therein through which air may pass from theinterior of said tubular member into said flotation cell, and a conduitcon-- necting the interior of said tubular member with a source ofpressured air.

4. Flotation cell apparatus comprising a vertical rigidwalled laterallydiverging conduit having a substantially centrally positioned bottominlet and an overflow adjacent to the upper end, an outflow conduitconnected to a lower portion of said flotation cell, a density controlvalve, said valve being in said outflow conduit operativc ly connectedto the interior of said flotation cell to regulate withdrawal ofmaterial from said cell to maintain substantially constant density ofpulp within the lower portion of said cell, a substantially verticalinflow conduit connected to the bottom inlet of said diverging conduitfor introducing a stream of fluid vertically upward into said flotationcell, and aerating means carried by the diverging conduit adjacent theconduit wall and providing a plurality of spaced generally horizontallyarranged apertures encircling said stream of fluid, said aerating 7means being disposed above the outflow end of said inflow conduit andbelow said overflow to efliect a substantially uniform distribution ofair bubbles across a horizontal cross section of the cell when theflotation cell is in operation.

5. Flotation cell apparatus as recited in claim 4 wherein said aeratingmeans providing a plurality of apertures is formed by a plurality ofholes extending through the diverging walls of said diverging conduitand through which air may pass into said flotation cell.

References Cited in the file of this patent UNITED STATES PATENTSAndrews Mar. 12,

Price Jan. 3,

Peterson Feb. 5,

Gibbs Nov. 30,

FOREIGN PATENTS Germany Sept. 20,

1. FLOTATION CELL APPARATUS COMPRISING A VERTICAL RIGIDWALLED LATERALLYDIVERGING CONDUIT HAVING A SUBSTANTIALLY CENTRALLY POSITIONED BOTTOMINLET AND AN OVERFLOW ADJACENT TO THE UPPER END, A SUBSTANTIALLYVERTICAL INFLOW CONDUIT CONNECTED TO THE BOTTOM INLET OF SAID DIVERGINGCONDUIT FOR INTRODUCING A STREAM OF FLUID VERTICALLY UPWARD INTO SAIDFLOTATION CELL, AND AERATING MEANS CARRIED BY THE DIVERGING CONDUITADJACENT THE CONDUIT WALL AND PROVIDING A PLURALITY OF GENERALLYHORIZONTALLY ARRANGED APERTURES ENCIRCLING SAID STREAM OF FLUID, SAIDAERATING MEANS BEING DISPOSED ABOVE THE OUTFLOW END OF SAID INFLOWCONDUIT AND BELOW SAID OVERFLOW TO EFFECT A DISTRIBUTION OF AIR BUBBLESACROSS A HORIZONTAL CROSS SECTION OF THE CELL WHEN THE FLOTATION CELL ISIN OPERATION.